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Wet etching of Silicon nitride (Si3N4) by phosphoric acid (H3PO4) is one of the key steps in the semiconductor fabrication process, especially for three‐dimensional integrated circuits (ICs). Unfortunately, few systematic studies of phosphoric acid etching of Silicon nitride are available. Summarizing how various factors affect etching and determining the reaction mechanism behind the etching process will help further optimize the etching process. In this work, how the boiling point of hydrous phosphoric acid solutions depends on phosphoric acid concentration is firstly investigated. Next, the etching of over 100 samples of Silicon nitride by H3PO4 at different concentrations and temperatures is systematically studied. The results show that the etching rate increases nearly linearly in both temperature and H3PO4 concentration, while temperature play more important role as compared to concentration. For each concentration, the reaction rate is maximal at the boiling point of the hydrous H3PO4 solution. Moreover, the etching rate of 85 wt % phosphoric acid is analyzed using the Arrhenius equation, yielding an apparent activation energy Ea=57.28 KJ/mol. Finally, a mechanism of Silicon nitride etching in phosphoric acid is proposed which explains the prior studies well. This work contributes to precisely control semiconductor processing for three‐dimensional ICs. [ABSTRACT FROM AUTHOR]

The modulation of the surface of silicon stimulates its applications in optics (antireflection surface, solar cells, and photoelectric devices). In this work, an appropriate ratio of the O2 to SF6 plasma through reactive ion etching generated a double-layer Silicon nanograss (upper layerflocculent SiOxFy passivation; lower layerpointy silicon spike) on the surface of the silicon wafer. The height and density of Silicon nanograss can be controlled through process parameters (pressure, O2/SF6 ratio, and RF power), mask spacing, and a variety of assistant substrates. The underlying formation mechanisms of Silicon nanograss disclosed that the sputtering of Al substrate acts as a micromask, i.e., primarily responsible for the formation of Silicon nanograss. Considering an in-depth study, a simple, low-cost, and CMOS-compatible method for wafer-level preparation of Silicon nanograss is provided. Specifically, the Silicon nanograss exhibited excellent antireflection and enhanced absorption properties. This work contributes to micro-nano surface science accompanied by optical applications. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated the association between maternal serum uric acid-to-creatinine ratio (SUA/SCr) in the first trimester and adverse maternal and neonatal outcomes. Methods: A prospective birth cohort study was conducted between 2018 and 2021. Logistic regression models and restricted cubic splines were utilized to estimate the associations between the SUA/SCr ratio and feto-maternal pregnancy outcomes. Women were stratified according to maternal age and pre-pregnancy body mass index. Results: This study included 33,030 pregnant women with live singleton pregnancies. The overall prevalence of gestational diabetes mellitus (GDM), pregnancy-induced hypertension (PIH), cesarean delivery, preterm birth, large-for-gestational age (LGA), small-for-gestational age, and low Apgar scores were 15.18%, 7.96%, 37.62%, 4.93%, 9.39%, 4.79% and 0.28%, respectively. The highest quartile of SUA/SCr was associated with the highest risk of GDM (odds ratio [OR] 2.14, 95% CI 1.93-2.36), PIH (OR 1.79, 95% CI 1.58-2.04), cesarean delivery (OR 1.24, 95% CI 1.16-1.33), and preterm birth (OR 1.30, 95% CI 1.12-1.51). The associations between SUA/SCr with adverse pregnancy outcomes showed linear relationships except for GDM (P < 0.001 for all, P < 0.001 for non-linearity). Subgroup analyses revealed that the associations between the SUA/SCr ratio and the risks of PIH and LGA were significantly stronger in younger pregnant women (P = 0.033 and 0.035, respectively). Conclusion: Maternal SUA/SCr levels were associated positively with the risk of adverse pregnancy outcomes. Timely monitoring of SUA and SCr levels during early pregnancy may help reduce the risk of adverse pregnancy outcomes and provide a basis for interventions., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)